Surgical lesion removal has traditionally been performed using a variety of surgical tools and techniques, some of which are specially adapted for a particular procedure. For example, large lesion removal from, e.g., the human breast, is typically attempted through an open incision using an ordinary surgical knife or scalpel. While the use of scalpels is widely accepted, they are not designed to minimize the invasiveness of a surgical procedure. During a surgical procedure, it is usually necessary to form an incision which is much larger than the lesion which is targeted for removal, so that the surgeon can work around, under, and over the lesion to remove both the entire lesion and a margin of tissue surrounding the lesion. The removal of a margin of tissue around the lesion is typically indicated, to be more certain that all of the lesion has been removed by the surgical procedure.
While the practice of removing tissue adjacent to a tissue mass of interest, e.g., a malignant or benign lesion, is followed in many lumpectomy procedures, the tools provided for a surgeon to remove the tissue are not well suited for performing the procedure. Straight and sculpted blade scalpels do not assist the surgeon in making the smallest cut necessary, and often require the surgeon to essentially dig out the tissue mass. The damage to the remaining tissues can be significant, resulting in considerable postoperative pain, excessive bleeding, long recovery times, the potential for infection, the potential for depression of the tissues at the surgical site (poor cosmesis) due to the removal of excessive tissue, and surface tissue scarring which is much larger than necessary. Furthermore, use of these conventional tools and techniques may cause excessive damage to the removed tissue and thus create a tissue specimen having ragged and irregular margins or borders. This, in turn can lead to inaccurate pathology studies of the excised tissue. There are some practitioners who believe that a significant number of negative pathology reports (i.e. reports which indicate that the specimen margins are clear of malignant tissue) are false negatives that will most likely result in recurrence of cancer in the patient. It is felt that a surgical device that results in smooth uniform margins would result in far more accurate pathology reports, particularly with patients who have or who are thought to have breast cancer. Patient management based on these more accurate reports would in turn lead to lower recurrence in breast cancer patients.
Breast cancer is presently the most common cancer in women and is the second leading cause of cancer deaths in women. With approximately one in eight American women developing breast cancer sometime in her lifetime, it is apparent that improved methods of diagnosis, such as breast biopsy are needed.
Electrosurgical devices have previously been used for tissue cutting, and surgical procedures. However, such devices typically use small, often pointed active cutting surfaces and the types of devices available to the surgeon who uses electrosurgery are limited. Furthermore, breast tissue and various other tissues are heterogeneous tissues and contain a variety of tissue types such as connective tissue, glandular tissue, vascular tissue, and adipose (fatty) tissue. Connective glandular and vascular tissues have similar characteristics in the way they react to high frequency electrical energy and hence the electrosurgical device. However, adipose (fatty)) tissue presents a higher impedance to the flow of electrical current than do the other types of tissues, and presents more difficulty in cutting. Thus, during an electrosurgical procedure if fatty tissue is encountered, a surgeon must perform surgical cuts by xe2x80x9cfeatheringxe2x80x9d, making repetitive shallow cuts over the same area to attain a desired depth of cut. These repetitive shallow cuts expose the patient to an increased risk of receiving an unnecessary amount of electrical energy, greater injury to surrounding tissues, greater risk of infection, as well as potentially creating ragged or irregular margins in biopsied tissues.
From the discussion above, it should be apparent that there is need in the art for more effective surgical cutting devices which lead to less trauma to the surrounding and biopsied tissues and which can provide biopsy specimens having smooth regular margins. Furthermore there is a need in the art for additional types of tools used in electrosurgery which give the operator greater control over the types and configurations of cuts made in tissue during a surgical procedure. The present invention fulfills these needs.
The invention is directed generally toward an electrosurgical device for cutting tissue, and the method of use, which is particularly suitable for cutting heterogeneous tissue such as found in breast tissue.
The electrosurgical device embodying features of the invention has a handle and an elongated cutting electrode which is secured to the handle and which is configured to be electrically connected to a high frequency power source. The cutting electrode is an elongated conductive member with a free distal end and is preferably manually shapeable. The cutting electrode has an exposed cuffing length of at least 0.5 inch (1.3 cm), and may extend up to 4 inches (10.2 cm). Preferably, the cutting electrode can have an exposed length ranging from about 0.8 inch to about 2.8 inches (2-7 cm). In other embodiments, the cutting electrode can have an exposed length in the range of about 1.2 inches to about 2.5 inches (3-6.4 cm). The elongated cutting. electrode may be provided with an exterior insulating jacket which is slidable along the cutting electrode to allow the operator to adjust the length of the cutting electrode which is exposed.
The cutting electrode has a maximum transverse cross-sectional dimension of about 0.007 to about 0.03 inch (0.18-0.76 mm), preferably about 0.008 to about 0.02 inch (0.2-0.5 mm). Elongated cutting electrodes having transverse dimensions of this magnitude may cut large areas of tissue, particularly adipose tissue, with a very effective xe2x80x9cclean sweeping motionxe2x80x9d with very little pressure against the tissue, thereby creating less trauma to the surgical site and providing for smoother margins of excised tissues. For increased electrode flexibility, the distal section of the cutting electrode may be distally tapered to smaller transverse dimensions. For example, the distal section may taper from a transverse dimension of about 0.01 to about 0.02 inch (0.25-0.51 mm) at the proximal section of the electrode to a smaller transverse dimension of about 0.004 to about 0.01 inch (0.1-25.4 mm) at a distal end of the tapered distal length.
A cutting electrode embodying features of the invention is formed of a conductive material and is preferably formed of a high strength metallic material such as tungsten, and alloys thereof and particularly tungsten alloys containing about 3 to about 25% (wt %) rhenium. The tungsten containing cutting electrodes are very suitable with high frequency electrical power. In alternative embodiments which operate at lower frequencies (e.g. less than about 2 megahertz) the electrode may be made of stainless steel and other metallic compositions.
The electrosurgical devices are preferably part of an electrosurgical system which includes a high frequency (e.g. RF) electrosurgery generator that is electrically coupled to the electrosurgical device. The high frequency generator is preferably configured to produce electrical power in a frequency range of about 1 to about 10 megahertz, particularly a frequency range of about 3 to about 8 megahertz with a current output of up to 4 amps. The voltage capacity is about 150 Vrms to about 800 Vrms to facilitate a wide variety of procedures, including coagulation at the lower voltages (e.g. about 150 to about 300 Vrms) and heterogeneous tissue cutting at the higher voltages (e.g. about 400 to about 800 Vrms). When cutting through heterogeneous tissue the voltage is controlled to a first range of about 550 to about 650 Vrms, typically about 600 Vrms during the initiating of the cut and then controlled at a lower level between about 450 and about 550 Vrms, typically about 480-500 Vrms. Amperage also may vary between initiation, e.g. about 1.75 amps, and normal running, e.g. about 1 amp.
The duty factor and the voltage generally should be higher at the initiation of the cut and less during the running period. For example, the duty factor may range from about 2 to about 10% up to 100% at a frequency of about 10 Hz up to the output frequency; however, generally the duty factor frequency is above 30 kHz with 50 kHz being typical.
The high frequency output of the electrical power generator has a periodic output and preferably has an essentially sinusoidal waveform and most preferably with a total harmonic distortion of less than about 5%. To complete the electrical circuit at least one additional electrode is needed to be in contact with the patient for a monopolar electrical configuration or on the electrosurgical cutting device for a bipolar mode. In one version of the invention the system has an electrode pad which is secured to the patient""s exterior close to the electrosurgical site to complete the electrical circuit.
The power cable directing high frequency electrical power from the electrical generator should be shielded cable and be flexible enough so that it does not interfere with the physician""s (or other operator""s) handling of the electrosurgical device during the procedure. One cable construction which has, been found to be very suitable has a central metallic conductor disposed within an outer jacket with a space between the central conductor and the inner surface of the jacket in order to reduce cable capacitance. The jacket has an outer polymer layer, an inner polymer layer and a shielding layer such as metallic braid, spiral wrap or foil disposed between the inner and outer layers. The inner polymer layer is essentially non-conductive. The central conductor is not supported within the jacket, it is essentially free floating, so it will contact the inner surface of the jacket at multiple locations when the cable is bent during use. However, the capacitance of the cable remains relatively constant because the off-center conductor averages to be the same as an on center conductor.
The invention may also be directed toward a method of performing tissue excision wherein an electrosurgical device is provided having a shapeable elongated electrode with a proximal end that is electrically connected to a high frequency power source and a distal end have a length of exposed cutting surface. The device preferably has a handle configured to hold the electrode and preferably have a mechanism to extend a desired length of exposed electrode out the distal end of the handle for a particular use. The elongated cutting electrode may be preshaped to a desired configuration in its manufacturing process or it may be manually shaped by the physician or other operator just prior to or during the procedure. The cutting electrode is placed in contact with the tissue to be excised and the electrosurgical device is then energized by providing RF power to the cutting electrode from a high frequency power generator. The cutting electrode will readily and smoothly pass through a variety of tissue types including muscular, connective, glandular and fatty tissue. The electrosurgical device may also be energized by the high frequency power generator with wave forms suitable for coagulation of bleeding vessels and tissue. A finger actuated switch on the handle or a dual foot switch situated on the floor allow the user to choose the cutting or the coagulation modes. Other modes may also be provided for other procedures.
These and other advantages of the invention will become more apparent from the following detailed description thereof and accompanying exemplary drawings.